Physics / Fizik
Permanent URI for this collectionhttps://hdl.handle.net/11147/6
Browse
3 results
Search Results
Article Citation - WoS: 28Citation - Scopus: 30P3HT-graphene bilayer electrode for Schottky junction photodetectors(IOP Publishing Ltd., 2018) Aydın, Hasan; Kalkan, Sırrı Batuhan; Çelebi, Cem; Çelebi, Cem; Varlıklı, Canan; 04.05. Department of Pyhsics; 04.04. Department of Photonics; 04. Faculty of Science; 01. Izmir Institute of TechnologyWe have investigated the effect of a poly (3-hexylthiophene-2.5-diyl)(P3HT)-graphene bilayer electrode on the photoresponsivity characteristics of Si-based Schottky photodetectors. P3HT, which is known to be an electron donor and absorb light in the visible spectrum, was placed on CVD grown graphene by dip-coating method. The results of the UV-vis and Raman spectroscopy measurements have been evaluated to confirm the optical and electronic modification of graphene by the P3HT thin film. Current-voltage measurements of graphene/Si and P3HT-graphene/Si revealed rectification behavior confirming a Schottky junction formation at the graphene/Si interface. Time-resolved photocurrent spectroscopy measurements showed the devices had excellent durability and a fast response speed. We found that the maximum spectral photoresponsivity of the P3HT-graphene/Si photodetector increased more than three orders of magnitude compared to that of the bare graphene/Si photodetector. The observed increment in the photoresponsivity of the P3HT-graphene/Si samples was attributed to the charge transfer doping from P3HT to graphene within the spectral range between near-ultraviolet and near-infrared. Furthermore, the P3HT-graphene electrode was found to improve the specific detectivity and noise equivalent power of graphene/Si photodetectors. The obtained results showed that the P3HT-graphene bilayer electrodes significantly improved the photoresponsivity characteristics of our samples and thus can be used as a functional component in Si-based optoelectronic device applications.Article Citation - WoS: 11Citation - Scopus: 11The Effect of Adsorbates on the Electrical Stability of Graphene Studied by Transient Photocurrent Spectroscopy(American Institute of Physics, 2018) Kalkan, Sırrı Batuhan; Aydın, H.; Çelebi, Cem; Çelebi, Cem; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of TechnologyAdsorbate induced variations in the electrical conductivity of graphene layers with two different types of charge carriers are investigated by using the Transient Photocurrent Spectroscopy (TPS) measurement technique. In-vacuum TPS measurements taken for a duration of 5 ks revealed that the adsorption/desorption of atmospheric adsorbates leads to more than a 110% increment and a 45% decrement in the conductivity of epitaxial graphene (n-type) and chemical vapor deposition graphene (p-type) layers on semi-insulating silicon carbide (SiC) substrates, respectively. The graphene layers on SiC are encapsulated and passivated with a thin SiO2 film grown by the Pulsed Electron Deposition method. The measurements conducted for short periods and a few cycles showed that the encapsulation process completely suppresses the time dependent conductivity instability of graphene independent of its charge carrier type. The obtained results are used to construct an experimental model for identifying adsorbate related conductivity variations in graphene and also in other 2D materials with an inherently high surface-to-volume ratio.Master Thesis The Effect of Atmospheric Gases on the Electrical Stability of Graphene(Izmir Institute of Technology, 2017) Kalkan, Sırrı Batuhan; Çelebi, Cem; Çelebi, Cem; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of TechnologyIn this thesis, adsorbate induced variations in the electrical conductivity of graphene layers with two different types of charge carriers are investigated experimentally by using Transient Photocurrent Spectroscopy (TPS) method. In-vacuum TPS measurements taken for a duration of 5 ks, revealed that the adsorption/desorption of atmospheric adsorbates leads to a 45 % incerment and 110 % decrement in the conductivity of CVD graphene (p--type) and epitaxial graphene (n-type) layers on semi-insulation (SI) Silicon Carbide (SiC) substrates, respectively. The graphene layers on SI-SiC substrates are encapsulated and passivated with thin SiO2 film grown by Thermal Evaporation and Pulsed Electron Deposition (PED) techniques. The mesurements conducted for short periods and a few cycles showed that the thermal passivation of graphene layers is insufficient. However, the PED encapsulation process completely suppresses the time-dependent conductivity instability of graphene independent of its charge carrier type. The obtained results are used the construct an experimental model for identifying adsorbate related conductivity variations in graphene and also in other 2D materials with inherently high surface-to-volume ratio.